Level transmitters, as a rule, exhibit an arm for signal transmission, on one end of which a float is placed, while the other end is pivotally secured to a carrier which in turn is anchored to base. Present on this secured end is a rivet contact element, which by at least one contact rivet, stands electrically in slide-contact with an arc shaped conductor path on a thick-film resistance. The conductive path is subdivided into individual stages aligned concentrically toward the center of curvature of the arc. Each stage is electrically connected to a resistance path. In accordance with the angular position, that is, as to the placement of the arm on the arc, the contact finds itself on another stage and thereby at another position on the resistance path, thus exposing the circuit to differing values of resistance. By point by point calibration, the values of resistance are converted to values of the content of the vehicle tank.
The thick-film resistance for the transmission device has a carrier, which is, for instance, made of ceramic material, upon which is imprinted a resistance path and at least one of the arc-like conductive paths contacted by the contact rivet. The conductive paths are constructed of an electrically conductive material.
EP 78 92 31 A2 discloses a tank content transmitter, in which two conductive paths of a thick-film resistance are provided to be contacted by contact fingers. In this case, the fingers are of a material composed of 38 wt % silver, in addition to palladium, platinum and copper.
In recent times, such fuel level transmitters have been, in part, subject to signal transmission error and even total failure, after a short operational life. In failure, the level transmitters deliver no electrical signal. These disturbances occur when the level transmitters are applied in fuel tanks made of fluoridized polyethylene and/or when desulfurized fuels are used.